Properties of fly ash concrete containing tropical soil bacteria

Abstract

The autonomous crack healing process using microbiologically induced calcium carbonate precipitation (MICP) is a sustainable alternative to overcome propagation of micro-cracks and restore the durability of concrete. This paper presents the potential use of tropical soil bacteria as a self-healing agent for fly ash concrete. A solution of 107 cells/mL Lysinibacillus sphaericus (L. sphaericus), was selected to be the self-healing agent by replacing partially the amount of water. Concrete cube specimens with 30% fly ash, were cured under two conditions, which are water and air curing. The potential effects of the self-healing agent was evaluated in terms of the ultrasonic pulse velocity (UPV), initial surface absorption test (ISAT) and compressive strength. The initial results show an improvement of UPV and between 12% and 54% improvement on the compressive strength for the bacterial concrete compared to the control specimen. It was probably due to the presence of the microbial calcium carbonate that fills the concrete pores through the inclusion of bacteria in the concrete. However, based on the ISAT value, the direct addition of bacterial solution increased the concrete’s permeability. Thus, further investigation is suggested to assess the self-healing effect towards permeability and compressive strength of bacterial concrete.